Vacuum advance issues

[Wrenchbender Ret]

The 307 was designed as a low emission engine. The factory initial timing was about 2 degrees. You will need to set the timing back far enough to prevent ping as it will destruck the engine & then tune from there. As I said brfore engine vary. Some work better with the vacuum on the manifold & some with ported vacuum. The larger trucks didn't have vacuum advance & they run fine. They are not concerned about part throttle cruiseing economy because they pulling all the time. You will have to use trial & error. There has been a lot of discution on this subject in these posts & other websites also. The car manufactures have made them both ways.